Method and apparatus for automatic lapping of piston rings



March 22, 1960 Filed Nov. 13. 1956 E. c. AUMILLER 2,929,174

METHOD AND APPARATUS FOR AUTOMATIC LAPPING OF PISTON RINGS 3 Sheets-Sheet 1 g/ Ezzmz Mar-Ch 22, E Q AUMILLER 2,929,174

MTHOD AND APPARATUS FOR AUTOMATIC LAPPING OF' PISTON RINGS March 22, 1960 E. c. AUMILLER METHOD AND APPARATUS FORI AUTOMATIC LAPPING OF' PISTON RINGS Filed Nov. 13, 1956 :s sheets-sheet :s

lllllllllll METHOD AND APPARATUS FOR AUTOMATIC LAPPING OF PISTON RINGS Edwin C. Aurniller, Crave Coeur, Mo., assignor to Ramsey Corporation, St. Louis, Mo., a corporation of Missouri Application November 13, 1956, serial No. 621,649

17 claims. (c1. s11s1) This invention relates to a method of and apparatus for the automatic lapping of piston rings.

Piston rings are used with pistons to create seals between the piston and the cylinder in which the piston is operating in a wide variety of devices. Perhaps the best known is within reciprocating internal combustion engines, such as are used on automobiles. It is Well known that rings should contact the cylinder over the entire periphery of the ring with a small degree of tightness. To insure this feature in the production vof piston rings, the rings should be properly tensioned, should be iiat, and should have an extremely smooth periphery. The smoothness at the periphery should extend across its entire width so that the cylinder can contact the ring face. Many rings are made with square faces, but some are made out of square or dierently for some specific reason.

Once installed in the complete device, the ring functions to seal the cylinder pressure from the crank case or to control oil flow from the -crank case to the cornbustion chamber. It is known that longer life may be obtained by chrome plating the outer face of the rings. The outer face of either the plain or chrome plated rings may be interrupted by grooves or may have a coarse thread finish to add scufl-resistance. Typically, the outer face is square but it may be desired to have the outer face tapered for installation as a lower compression ring with the scraping edge downward. Thus compression rings all present either a plated or unplatedvfacc and either a square or tapered face. Oil control rings may have various bevels and grooves, but nevertheless, they do present narrow faces which bear against the cylinder walls.

A common problem to all these different basic ring designs is found in the method and apparatus used in providing at manufacture a smooth cylinder contacting face. Typically this is done by lapping.

In the past, it has been customary to manu-ally load groups of rings onto suitable arbors or mandrels which are then installed in a lapping machine. While this method is superior to lapping one ring at a time by hand, it has been found that a still quicker and lower cost method and apparatus for lapping piston rings can be obtained by using an automatic lapping machine which handles but one ring at a time. This machine operates in accordance with a method and is constructed in accordance with principles described herein. An economy is achieved in that manual loading and unloading is eliminated, a more uniform lapped finish is produced, and a lesser number of lapping strokes is required.

Accordingly, I have found that a superior method for lapping piston rings comprises simultaneously picking up and radially compressing the ring to its operating diameter, thereby restraining it; lapping the surface of the ring while it is so restrained and then releasing the ring by removing the external restraint. I have also found that one particular form of apparatus performs this method especially well which comprises a pot having arent C an opening with a circular cross-section, a frusto-conical surface at one end of the opening and an enlargement at the opposite end of the opening. Within this opening there moves a plunger which has a tapered end to center the ring, a shoulder which coacts with the frustoconical portion of the opening to compress the ring squeezing it into a peripheral groove in the plunger,y together with the associated equipment for driving the plunger and feeding unlapped rings to the apparatus.

Accordingly, it is an object of this invention to provide a method for picking up, lapping, and -releasing a piston rmg.

Another object of this invention is to provide means for radially compressing and picking up the ring, restraining and lapping the ring, and releasing the ring.

A further object is to provide a pot and plunger cooperative with said pot for picking up, lapping and releasing a piston ring.

Yet another object is the provision of an apparatus of the type described which will automatically lap piston rings individually.

A further object is the provision of an apparatus for picking up and lapping piston rings.

A still further object is the provision of a lapping machine which laps rings with both reciprocating and rockable motion.

Yet another object is the provision of a lapping machine for piston rings which has a release means for not only releasing but catching rings as they are snapped free.

A. still further object is the provision of a lapping .i

machine for square-faced piston rings.

Another object is the provision of a lapping machine for taper-faced piston rings.

Still another object is the provision of a lapping machine capable of automatically picking up lapping and discharging individual piston rings.

Another object is the provision of a lapping machine which is automatically fed piston rings to be individually lapped.

Other objects, features and advantages of this invention will be apparent from the following detailed description of the attached sheets of drawings, which by way of a preferred embodiment and a modification thereof illustrates the invention.

On the drawings:

Figure l is an elevational view of an automatic lapping machine for piston rings;

Figure 2 is a top view of the machine shown in Figure 1 on a slightly reduced scale;

Figure 3 is an enlargement of a portion of Figure l, partly in section and partly in elevation, showing the plunger immediately prior to its picking up' a ring;

Figure 4 is similar to Figure 3 except that the plunger is shown with the piston ring during one of the lapping strokes;

Figure 5 illustrates a modified lapping surface otherwise similar to Figure 4; and

Figure 6 schematically illustrates a modied form the instant invention.

As shown on the drawings:

Referring to Figure l, there is shown a schematic presentation of an elevational view of an automatic lapping machine constructed in accordance with this invention. The machine is illustrated as having a support 10 which carries a lapping pot 11, a power drive and plunger assembly 12 and a feed mechanism 13.

The support 10 may be constructed in any convenient way. The lapping pot 11 is placed over a hole in support 10 (not shown). In line with this hole and with the lapping pot, is a rack or spindle 14 onto which the lapped rings are discharged. The pot 11 hasan openj ing having a circular cross-section and extending through the pot, such opening being generally indicated by the numeral 15. At the upper end of the opening7 there is a frusto-conical surface 16 while at the opposite end of opening 15, there is an enlarged portion i7, the Ydiameter of which exceeds that of the piston ring in its free state. As will be shown later, this enlarged portion IS7 is optional, but preferable.. The lapping pot 1i may be `made of a single piece or it may be comprised oi an insert within a holding structure as shown in Figures 3 the latter form being preferable.

The piston and drive assembly 12 is carried by the support lil and is made up of a conventional actuating cylinder assembly 18. As shown, a piston rod 19 projects from both endsof the drive cylinder. It will be seen that the apparatus shown connected to the upper end of piston rod 19 could also be attached at the opposite end of the piston rod, thereby enabling utilization of a drive cylinder having a piston rod which comes out of one end only. Secured to the upper end of piston rod 19 is a head 2G which is engageable with conventional electrical limit switches S21-245, earch of which are stationary with respect to the housing and to the casing of the power drive 18. At the opposite end of piston rod 19, there is shown a plunger or piston 2.5 which is rigidly secured to the piston rod 19. The structure is so arranged that power drive 18 acting through the piston rod 19 may reciprocate piston or plunger 25 through the opening without contacting the same. piston rod 19 and plunger Z5 vmay not only be reciprocated asa unit, but also 'may be rotated or rocked as a unit. Head 20 is 'provided with a pair of pins Z625 which straddle a curved rod 27. Rod 27 has a straight portion at its upper end and may have a cam surface engageable by pins 26426 whenever the head is so positioned anywhere between limit switches 252 and 2.3. The cam rod 27 is stationary with respect to housing 1i). lt can be seen that the pins 26 may be carried by the opposite end of piston rod 19 such as by plunger 25 if reshaped to continuously extend out of circular cross-section opening 1S.

Referring to Fig. 3, the plunger or piston is illustrated as being threadably engaged with piston rod 19. The mode of attachment is not important, it being preferable, however, that the piston be removable for ease of manufacture and assembly. Thus shoulders, washers, bushing, nuts and the like might also be used in making this connection in any manner. its leading end a frusto-conical portion 28. r`he widest portion of the frusto-conical portion has a diameter which is less than the smallest inside diametral measurement-of the ring to be lapped when the ring is in its uncompressed or free state. Thus when the plunger 25 is brought into the truste-conical portion 16 of the lapping pot 11, the frusto-conical portion 28 will cause a piston ring lying in the frusto-conical portion 1o to be centered. The widest portion of the truste-conical por-tion 2S also defines one edge of a groove 29. The other edge of groove 29 is formed by a shoulder Stia which extends outwardly from the piston rod but terminates in spaced relation to the narrowest portion ofL cylindrical opening 15. The specific dimensions chosen will be selected on the basis of the dimensions of the ring to be lapped.

Referring to Figs. l and 2, a feeding mechanism is shown as being part of the lapping'machine, the details of whiclrfeeder are notpart of this invention. Any other feeding mechanism'capable of performing the same functions as performed by the one shown herein, may be used in place thereof. For purposes of illustration, a brief description of the instant feeding mechanism will be given. The feeding mechanism 13 is comprised of a base portion 30 which is stationary with respect to support 1li. Secured to the base 30 are three upstanding ring guides 31, 32 and 33. These opstanding guides are here'shown `neatly 'aligning astackof rings 34 to be and 4,

Theplunger 25 has at v lapped. Base .30 has a longitudinal slot (not shown) over which lies a slide plate which has a bracket 36 secured thereto and which extends below plate 35 through as shown in Fig. 3.

Head as, and i Electrical switches 2-2li, 39 and 4i) comprise one form of a synchronizing means. They are electrically interconnected between themselves to operate electric Valves which bring fluid energy to feed mechanism cylinder 38 and to the power drive cylinder 1S. The power `to these electric switches and to the solenoid valves (not shown) which control the fluid energy is further controlied by an electricalrsequential timer (also not shown) which either permits a certain number of lapping strokes by power drive 1S or which permits power drive 18 to reciprocate for a predetermined length of time. Of course a stepping switch-limit switch could be used at 22 or 23 to totaiize the strokes in place of a timer.

At thebeginning of the cycle,the feed mechanism 13 takes the lowermost of the stack of piston rings 34 and slides it into the truste-conical end of opening 15 of lapping pot l1. When plate 35 reaches the end of its stroke, bracket 3o engages limit switch itl which Vis connected to cause the return of slide plate 35. When slide 35 reaches its retracted position, bracket 36 engages limit switch 39 which upon engagement, permits the movement of piston rod 19 in a downward direction from the position shown in Figure l. Y

When plunger 25 moves downward from its retracted position outside of the opening 15, it enters the opening 15 as shown in Figure 3. lf piston ring 34a is not properly centered, frusto-conical surface 2h causes the ring to become centered by entering the ring opening. Thereafter shoulder 36a engages ring 34a and continues moving in a downward direction, thereby cooperating with frusto-conical surface 16 to inwardly move or compress the piston ring 34a into groove 2g. As the downward movement continues, the compressing of the piston ring also continues until it reaches the diameter dened by thecentral or lapping portion of opening 15. This opening preferably is'ol:` a size corresponding to the outside operating dimension of the piston ring. f.lhe motion ofv plunger 25 continues inwardly, thus Abeginning the actual lapping.

Upon engagement with or actuation of limit switch 23, the piston is caused to reverse its direction of motion until limit switch Z2 is engaged at which reversal again takes place. Reciprocation between limit switches 22 and 23 continues until the central control is satisfied (number of strokes or lapping time reached), whereupon switch 23 is shunted so that the piston 2S takes an extended downward stroke, terminated by limit switch 24 which in turn shunts switch 22. Thus the downward movement of the plunger is permitted to be extended so that groove 29 registers with enlarged portion 17 torelease the lapped ring. On its return stroke, the head2()` moves past the now shunted switch 22 to engage switch 231 to remain Athere until the next ring has been fed. Switch 21 alsorinitiates the next .feeding cycle.

By moving the groove 29 beyond the point indicated at numeral 41 in Figure 4, the restraint was removed from the piston ring, thereby enabling it to snap outwarddue to its -own resiliency. Upon taking its original natural form, the ring immediately becomes freed of the frustoconical portion of plunger 25 and of groove 29. 'Ihis 1 transition condition is shown in dash lines in Figure 4 just before the ring 34a begins to fallaround theracli, guide or spindle 14.

From this description it is apparent that the substantial enlargement 17 ofthe opening 15 is not necessary for the automatic removal of the ring fromplunger 25. However it can be seen that if the ring should disengage from one side only, it would hang up in the groove 29. Therefore it is preferable to also have the substantially enlarged portion 17 which could mate with the newly lapped surface of the ring opposite to the point of such hang-up. This mating would come in the form of a springing blow at the time that the ring is released or that the restraint is removed, thereby causing the ring to be forced back or centered so as to fall freely out of the groove 29.

While piston rod 19 is being reciprocated between limit switches 22 and 23, pins 26, 26 engage the curved portion or cam 27, most clearly "shown in Figure 2. rIhis cam imparts a rotational movement to plunger 25 and hence to the ring being lapped.V This rotational or rocking movement prevents deep axial scratches on the lapped face'of the ring. It can be seen that this optional feature is highly desirable.

' It has been shown that when switch 23 was inactivated or shunted by ythe central control, that head 20 would continue past the limit switch 23 thus removing the restraint from the ring and releasing it. The downward movement of plunger 19 continues until head 20 reaches limit switch 24 which arrests the movement and causes its return to limit switch 21. Limit switch 21 is connected to cause feeding movement of slide plate 35, whereby the lapping program may be repeated indefinitely.

l In the form illustrated in Figures 1-5, the piston or plunger 25 is reciprocated, and the lapping pot 1l. remain-l ing stationary. In some forms of this invention, it may be desirable to reciprocate and/or rock the lapping pot, leaving the plunger 25 stationary. Such a structure is schematically illustrated in Figure 6, wherein the plunger 25 is rigidly supported in line with a reciprocable pot 15' and is provided with an actuating cylinder assembly 18', the pot 15 being shown at 'its lower limit of travel.

Referring to Fig. 5, there is illustrated a modified form of this invention. The lapping pot 11a has an opening i551 having a frusto-conical portion 16 and a substantially enlarged portion 17. It will be observed, however, that the central lapping portion of the opening 15a has been tapered slightly having its larger end 42 joined to the smaller end of frusto-conical portion 16 while its smaller end 43 terminates at enlarged portion 17. The diameter of plunger 25 must be such as to clear the walls at portion 43. By such a modification of the lapping pot 11, a tapered face on the ring may be lapped.

Thus it will be seen that a completely automatic lapping machine has been provided which may be used to lap the cylinder contacting faces of piston rings at a somewhat reduced cost over that which was previously possible. It will also be seen that a uniformly lapped nish Will be produced since each ring is Itreated exactly the same and since each works overthe same surface. The method of lapping rings as taught herein may be accomplished by numerous variations of the apparatus, including substantial departures therefrom. Accordingly, a method has also been shown how piston rings may be picked up, lapped and released more efficiently than they previously could be. It Will be seen that this method has been made particularly practical by the novel structure which has been provided to pick up and simultaneously compress the piston ring to its operating diameter, the lapping and release of the ring being also eiiiciently carried out.

' It will be understood that numerous modificationsV and variations may be effected without departing from the scope of Ithe present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

I claim as my invention:

1. A lapping machine for a piston ring comprising, in combination: means for radially compressing and thereby and thereafter picking up the ring to be lapped; means for both radially restraining and for lapping the ring While it is so compressed; and additional means for removing the radial restraint, thereby releasing the lapped ring from the machine.

2. A lapping machine for a piston ring comprising, in combination: radial compression means including a frusto-conical surface for engaging the piston ring to pick it up; means for both radiallyprestraining and for lapping the ring while it is so compressed; and means remote from said frusto-conical vsurface for removing the radial restraint, thereby releasing the lapped ring from the machine.

3. A lapping machine for a piston ring comprising, in combination: means for radially compressing and thereby and thereafter picking up the ring to be lapped; restraining means having a circular cross-section concentrically engageable with the ring for radially restraining the ring while it is so compressed; means ,for apply-V ing relative lapping motion to the ring while it is so restrained; and means disposed remotely from said compressing mean for removing the radial restraint, thereby releasing the lapped ring from the machine.

4. A lapping machine for a piston ring comprising, in combination: means for radially compressing and thereby picking up the ring to be lapped, restraining means having a circular cross-section concentrically engageable with the ring for radially restraining the ring while it is so compressed; means for applying relative lapping motion'to the ring while it is so restrained; and means for removing the radial restraint, thereby releasing the lapped ring; said last mentioned means comprising a substantial enlargement of the circular cross-section of said restraining means remote from said compressing means and into which said motion meansis adapted to move the ring.

5. A lapping machine for a piston ring comprising, in combination: radial compression means for picking up the ring including a frusto-conical surface for engaging the outer periphery of the piston ring before the ring is picked up; restraining means having a circular cross-section concentrically engageable with the ring for radially restraining the ring while it is so compressed;

means for applying relative lapping motion to the ring while it is so restrained; and means for removing the radial restraint, thereby releasing the lapped ring; said last mentioned means comprising a substantial enlargelment of the circular cross-section of said restraining means remote from said frusto-conical surface and into which said motion means is adapted to move the ring.l

6. A lapping machine for a piston ring comprising, in combination: a pot having an opening with a frusto-V conical surface blending at its smaller end into a circular cross-section lapping surface; and a plunger relatively axially movable into said opening for lapping the ring; said plunger having a peripheral shoulder and a periph eral ring groove, one edge of which is defined by said shoulder and the other edge of which is of lesser diameter and is iixedly spaced therefrom; said shoulder being located to cooperate with said frusto-conical surface to pick up the ring by compressing it into said n'ng groove, thus positioning it for lapping.

7. A lapping machine for a piston ring comprising, in combination: a pot having an opening with a frustoconical surface blending at its smaller end into a circular cross-section lapping surface; and a plunger relatively axially movable into said opening for lapping the ring; said plunger having a tapered end, the widest portion of which defines a first edge of a peripheral ring groove; said plunger also having a peripheral shoulder which defines a second edge of said ring groove; said shoulder being located to cooperate with said frusto-conical surface to 8. A lapping .machine for a piston ring comprising,

in combination: aipot'having an opening with a frustor conical .Surface blending at .its smaller-end into a circular cross-section lapping surface; vand a Aplunger having a ring receiving portion relatively axially movable into and completely lthrough the entire length of said opening ,for picking rup and lapping the ring at said frustoconicalandrlapping surfaces respectively, and fo-r releasing theringbyextending through said opening.

9.`A lapping machine lfor a -piston ring comprising, invcombination: 'a'pot -having an opening with a circular cross-section lapping surface; plunger means entering one end of said opening to pick up and lap the ring; and yrelease means at the other end'of said opening comprising a substantial enlargement -of said opening for releasing the ring from the machine, said plunger being exteudible into said last named means.

10,A lapping machine for a piston ring comprising, in combination: apot having an opening with a frustoconical surface blending at its smaller end into a circular cross-section lapping surface; a plunger relatively axially movable into and through the length of said opening for lapping the ring; said plunger having a tapered end, the Widest portion of which defines a first edge of a peripheral ring groove', said plunger also having a peripheral shoulder which defines a second edge of said ring groove; said'shoulder being located to cooperate with said frusto-conical surface to pick up the ring by compressing it into said ring groove, thus positioning it for lapping; and ,release-means at the other end of said opening comprising a substantial enlargement of said opening.

Y1l. A lapping machine for a piston ring comprising, in combination: `a pot having an opening with a -frustoconical pickup surface blending at its smaller end into the larger end of a frusto-conical lapping surface; and a plunger relatively axially movable into said opening and adapted to pick up and effect lapping ,movement of the ring.

l2. A lapping machine for a piston ring comprising, in combination: a pot having an opening with a circular` cross-section lapping surface; a relatively axially displaceable plunger movable into said opening and adapted to .both pick up yand reciprocatingly lap the ring; apin member; V'and a cam member engageable therewith; one of said members being carried for reciprocation by one of said plunger and pot, and bearing against the other member vand operative to rock said one of said plunger and pot about its axis while it reciprocatingly laps the ring.

v13. A lapping machine for a piston ring comprising, in combination: a pot having an opening with a frustoconical -surface blending at its smaller end into a circular cross-section lapping surface; a relatively axially displaceable plunger movable intoV and through the length of said opening; sad'plungerhaving a'tapered end, the widest Vportion'of which defines a first redge-OfapeIipheral ring groove, said vplunger also having a peripheral shoulder which defines a second edge of saidring groove; said shoulder beingflocated to cooperatewith said frustoconical -surface to pick up the ring by compressing it into said ring groove, thus positioning it for lapping; cam means acting on said :plunger to'rockit about its axis while it reciprocatingly laps the ring; and release means at the other end of said opening comprising a substantial enlargement of saidopening.

14. A method for lapping a piston ring comprising, the sequential steps of first radially compressing 'the ring to be lapped, thereby restraining it radially; sec ondly picking up v,the ring by effecting axial restraint; thereafter lapping a surface of the ring while .it yisso restrained; and releasing the ring by removing the radial restraint. Y

15. A method for lapping a piston ring comprising picking up the ring to be lapped by relatively moving it axially into engagement with converging and parallel surfaces of a lapping means, thereby also'compressing and restraining it radially; simultaneously therewith, restraining the ringaxially, lapping a surface of the ring while it is so restrained; and releasing the ring by'removing the radial restraint rWhile it is axially restrained.

16. lA method for lapping a piston ring comprising picking up the ring to be lapped by relatively moving it axially into engagement with converging and parallel surfaces of a lapping means, thereby also compressing and restraining it radially; simultaneously therewith restraining the ring axially; applying relative lapping motion to the ring while it is so restrained, said lapping motion comprising relative movement of the ring rockably about its axis and reciprocatingly along its axis and releasing the ring by removing the radial restraint before the axial restraint is removed.

17. A method for lapping a piston ring comprising picking up the ring to be lapped by moving it axially into engagement with converging and parallel surfaces of a lapping means, thereby also compressing andrestraining it radially; Simultaneously therewith restraining the ring axially; lapping a surface of the ring whilev it is so restrained; and releasing the ring by axially moving it Whileaxially restrained to aV point remote from said converging and parallel surfaces beyond Whichsaid lapping means lcannotr restrain it.

References Cited in the file of this patent UNlTED STATES APATENTS 550,785 Friend Dec. .3, 1895 2,195,056 WallaceV Mar. 26, 1940 2,422,418 Hutto June 17, 1947 2,679,129 Haldeman May 25, 1954 2,749,672 Haldeman June l2, 1956 2,765,529 Bolender Oct. 9, 1956 2,785,512 Hutto Mar. 19, 1957 

